A CPP (Current Perpendicular to plane)-GMR element employs a metal layer for a spacer layer thereof. The metal layer has lower resistance to make the CPP-GMR element more advantageous than a TMR element. However, there has been a problem that the CPP-GMR element cannot provide a sufficiently high MR change rate.
A configuration of the CPP-GMR element or a material of a spacer layer to be included therein has been modified in order to solve such a problem.
For example, JPA1997-147579 discloses that a spacer layer of the CPP-GMR element is not a simple metal layer but includes an oxide layer having a current path (NOL: nano-oxide layer). The current path allows a current to flow in a thickness direction of the oxide layer. The CPP-GMR element provides a CCP (current-confined-path) effect to enable it to increase an MR change rate. Such an element is called a CCP-CPP element.
In addition to the above disclosure, JPA2004-6589 discloses that a magnetoresistive element in which a thin-film spin filter (SF) layer is inserted in the magnetic layer or between the magnetic layer and a nonmagnetic spacer layer. The thin-film spin filter layer includes an oxide or a nitride. The SF layer provides a spin filter effect to prevent either an up-spin electron or a down-spin electron from passing therethrough, thereby enabling it to increase an MR change rate.